Re: [PATCH v2] i2c: designware: Do not complete i2c read without RX_FULL interrupt

Andy Shevchenko
2021-12-14T12:04:06Z

On Tue, Dec 14, 2021 at 02:00:59PM +0200, Andy Shevchenko wrote:
> On Tue, Dec 14, 2021 at 08:25:18AM +0530, tamal.saha@intel.com wrote:
> > From: Tamal Saha <tamal.saha@intel.com>
> >
> > Intel Keem Bay platform supports multimaster operations over same i2c

Here you put multimaster...

> > bus using Synopsys i2c DesignWare IP. When multi masters initiate i2c

...and here multi masters.

Be consistent.

I believe the best way is to use dash variant, i.e. multi-master(s),

> > operation simultaneously in a loop, SCL line is stucked low forever
> > after few i2c operations. Following interrupt sequences are observed
> > in:
> > working case: TX_EMPTY, RX_FULL and STOP_DET
> > non working case: TX_EMPTY, STOP_DET, RX_FULL.
> >
> > DW_apb_i2c stretches the SCL line when the TX FIFO is empty or when
> > RX FIFO is full. The DW_apb_i2c master will continue to hold the SCL
> > line LOW until RX FIFO is read.
> >
> > Linux kernel i2c DesignWare driver does not handle above non working
> > sequence. TX_EMPTY, RX_FULL and STOP_DET routine execution are required
> > in sequence although RX_FULL interrupt is raised after STOP_DET by
> > hardware. Clear STOP_DET for the following conditions:
> > (STOP_DET ,RX_FULL, rx_outstanding)
> > Write Operation: (1, 0, 0)
> > Read Operation:
> > RX_FULL followed by STOP_DET: (0, 1, 1) -> (1, 0, 0)
> > STOP_DET followed by RX_FULL: (1, 0, 1) -> (1, 1, 0)
> > RX_FULL and STOP_DET together: (1, 1, 1)
> >
> > Signed-off-by: Tamal Saha <tamal.saha@intel.com>
> > ---
>
> So, where is the changelog?

--
With Best Regards,
Andy Shevchenko